Accelerometers, such as Micro-Electro-Mechanical Systems (MEMS) accelerometers, are sometimes incorporated into portable electronic devices for determining the spatial orientation of the device or other uses. The manufacturing process for making accelerometers may result in misalignment of its sensing axes. In addition, the process of assembling an accelerometer into an electronic device often results in the accelerometer being misaligned (e.g., rotated and/or tilted) relative to a target orientation on the circuit board of the host device. Thus, built-in accelerometers may suffer from non-zero pitch and roll effects. Moreover, MEMS accelerometers are subject to a wide array of factors which create random offset errors. For example, heat, axial stress, and the adhesive underfill applied to fix the accelerometer to the circuit board of the portable electronic device may create errors in the differential capacitance measurement of the MEMS sensing part(s).
The improper alignment of a built-in accelerometer and errors in the differential capacitance measurement cause measurement errors in the accelerometer readings. Accordingly, built-in accelerometers typically require testing and calibrating to measure and correct measurement errors such as bias error. Calibration improves user interaction with the portable electronic devices by providing more accurate and repeatable accelerometer output to the operating system and applications of the portable electronic device using the accelerometer. However, the testing and calibrating of built-in accelerometers adds to the cost and time required to produce the host portable electronic devices. Accordingly, there exists a need for methods and systems for efficient testing and calibrating of built-in accelerometers.
Like reference numerals are used in the drawings to denote like elements and features.